Electromigration (EM) is the result of momentum transfer from electrons which move in the applied electric field, to ions which make up the lattice of the interconnect material. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures.
As the structure size in integrated circuits (ICs) decreases, the practical significance of EM effect increases. That is, continued miniaturization of ICs which are subject to increasingly high current become more prone to EM failure. For example, EM can lead to the electrical failure of interconnects and/or metal wiring in relatively short times, reducing the lifetime of the IC.
Thus, with the continuing aggressive scaling of interconnect dimensions and introduction of new lower k dielectric materials, the back end of the line (BEOL) interconnect reliability margins of EM is significantly reduced. In fact, EM is of increasing concern at new technologies because wire cross-section scales by 50% from each node, but circuit voltage and liner thickness do not scale at the same rate. Therefore, even greater current density is imposed for the interconnect wires at new technology nodes. Besides the geometry shrinkage, process induced challenges such as Cu microstructure degradation could further aggravate the EM problem.